1. Technical Field
The present invention relates to a manufacturing method of a semiconductor device and a semiconductor manufacturing device. Particularly, the invention relates to a manufacturing method of a semiconductor device and a semiconductor manufacturing device capable of decreasing scattering of a thermal history resulting in a semiconductor device during manufacture.
2. Related Art
FIG. 10 is a flowchart for explaining a currently available method of manufacturing a semiconductor device. The flowchart shows a process of forming a gate oxide film of a transistor through thermal oxidation of a silicon substrate by using an ordinary pressure thermal oxidation furnace. A thickness of the gate oxide film considerably affects transistor performance. Consequently, it is necessary to decrease scattering of the thickness of the gate oxide film.
On the other hand, since an atmospheric pressure is undergoing a change every minute, a partial pressure of oxygen inside the thermal oxidation furnace is also undergoing a change every minute. Hence, to keep the thickness of the gate oxide film at a fixed level, it is necessary to adjust heat-treating time, heat-treating temperature and the like in keeping with fluctuation of the atmospheric pressure. Examples of adjusting thermal oxidation time according to the fluctuation of the atmospheric pressure will be described as follows.
First, a silicon substrate is carried into the thermal oxidation furnace (S102). Next, a temperature of the thermal oxidation furnace is raised (S104). Further, the atmospheric pressure is gauged (S106), and oxidation time is determined according to the result of gauging (S108). Specifically, as the atmospheric pressure decreases, the oxidation time is extended.
When the temperature of the thermal oxidation furnace reaches a specified temperature (for example, 900° C.), by keeping that temperature as long as the determined oxidation time, a surface of the silicon substrate is thermally oxidized (S110). After a lapse of the determined time, the temperature of the thermal oxidation furnace is lowered (S112), and the silicon substrate after thermal oxidation is carried out (S114). Such technology is disclosed, for example, in Japanese Unexamined Patent Publication No. Hei7-74166.
In a case where the thermal oxidation time or the heat-treating temperature is made to change based on the fluctuation of the atmospheric pressure, the thermal history of the semiconductor substrate varies per lot. Therefore, there is a possibility of the characteristics of the semiconductor device being different per lot. Especially, in the case where an impurity is introduced into the semiconductor substrate prior to thermal oxidation, since a diffusion profile of the impurity is different per lot, there is a possibility that the electrical characteristics of the semiconductor device are different per lot.
Further, in CVD processing, pressure is a key parameter to determine a rate of deposition. In case of carrying out CVD under the ordinary pressure, to make the film thickness constant, the atmospheric pressure is gauged, while CVD processing time or processing temperature may sometimes be adjusted based on the result of this gauging. In this case, there is a possibility that even in the CVD processing under the ordinary pressure, the thermal history of the semiconductor substrate is different per lot and that the characteristics of the semiconductor device are different per lot.